Thoughts on the evolution of wireless networks and mobile web 2.0

Here's a link to an interesting post on Mobile Europe on the impact of IP applications running in the background on wireless networks. In short, the message is that despite instant messengers, e-mail applications and other connected programs running in the background require relatively little bandwidth, they nevertheless have a significant impact on the overall radio link capacity. So why is that, a reader recently asked me?

Let's make a practical example: On my Nokia N95, I use the VoIP client over Wi-Fi a lot. The client works in the background and every now and then communicates with the SIP VoIP server in the network to let it know that it is still there and to keep the channel open for incoming messages. This requires very little bandwidth as there are only few messages sent, from an IP point of view, about 2 a minute. For the full details, have a look at this earlier post.

From a 3G cellular radio network perspective, however, things look a lot different. There are two possibilities: The network could keep the radio link to the mobile device open all the time. This, however, would drain the mobile's battery very quickly as the mobile constantly has to monitor the link for incoming data. Further, this would waste a lot of bandwidth, since a full air interface connection requires a frequent exchange of radio link quality messages between the mobile and the base station. In other words, there is lots of overhead monitoring and signaling going on while no data is transferred.

The other option, usually used today, is to set the mobile device into a lesser activity state. In practice that means that in case little activity is detected by the network, channels are used which are not as efficient, but do not require constant radio link quality measurement reports and dedicated channel resources. That's already a bit more efficient but still consumes a lot of energy on the mobile side. For details see my earlier post on the "FACH power consumption problem". Some networks, which are configured well, detect that only little data is transferred and keep that state. Other networks immediately jump to the full channel right away when data is exchanged again which requires lots of radio link signaling. Further, in UMTS, the channel switching is organized by the Radio Network Controller and not in the base station itself thus putting quite a high burden on a centralized network element.

So what does this mean in practice? In networks today, a single base station covers around 2000 mobile devices. Not a problem today, as with traditional wireless voice, there is no ongoing signaling between the device and the network while there is no call. With non-wireless optimized VoIP however, as described before, there are 2 messages exchanged per minute per device plus potentially further radio interface signaling for channel switching and radio link measurements. In other words, such background IP packets have a higher radio link capacity impact than their size suggests compared to big IP packets that are part of a time limited high bandwidth data flow, e.g. while transferring a web page.

Now multiply that background traffic by 2000 devices per base station (assuming for a moment a pure IP world, non optimized) and you get 66 messages a second that need to be transmitted. Many of these require state changes, thus creating additional signaling in the network. Add to that IM, e-mail, etc., and the number will rise further.

Now why is this different to fixed line networks? There are two reasons: First, in fixed line DSL networks, there is usually only a single household behind a DSL line with only a few devices creating background noise. Second, in fixed networks no additional overhead is required for managing a shared transmission resource, i.e. the air interface. In other words, a small packet just takes that amount of bandwidth on the cable, no less, no more.

To be clear: I am not saying this is a problem for wireless networks (yet), it's just a lot more traffic in the background than what there used to be and it requires more bandwidth on the air interface than their size suggests. Also, standards are addressing this change of application behavior, for example with UMTS enhancements such as Continuous Packet Connectivity, or in LTE with transferring the radio state management from a centralized network element directly into the base station.

In any case I guess we'll see such always-on applications over time to be optimized for mobile use, i.e. more push than poll and less keep-alive signaling. But that's probably not done to please network operators or to increase overall network capacity but to reduce power consumption on the mobile devices.

This might seem obvious to most but I just realized these days how important the battery is for the mobile experience. I recently bought a netbook (see here and here) and while most experiences are positive, a battery lifetime of only 2 hours just doesn't do for me in many cases especially when I am traveling. Even if it is enough, connecting the netbook back to the mains all the time for recharging is also a hassle. So I bought an extension battery pack which gives me 6 hours of autonomy in addition to the 2 hours of the standard battery. An incomparable experience! Now even while traveling for a whole day, sitting in the train, waiting at the airport and on the plane, I don't have to worry about the netbook running out of power. Very nice!

I had an interesting surprise when I passed through Paris airport recently. Orange (France Telecom) has put a vending machine in the airport hall where people can buy prepaid SIM cards with different kind of phones and also prepaid 3G Internet access together with a 3G stick.

The Internet offer with the 3G stick (locked to the network operator I suppose) is around 30 Euros. Oddly enough from an outsiders view, usage is paid by time and not by volume. 2h are included in the starter pack.

Back in October 2008, I wrote about a blog post of David Wood, who is part of the Symbian leadership team, where he said that while smartphones only account for 10-15% of sales units, the sales revenue is between 20-25% and profits may even exceed 40%. Now Moco News reported similar numbers being given by Deutsche Bank analyst Brian Modoff in an article in the Wall Street Journal.

His numbers are as follows:

Apple and RIM together only have 3% of the mobile phone market share but make 35% of the total profits.

Nokia manufactured 46% of the mobile phones sold last year (I heard 38% somewhere else) and made 55% of the profits. Note: It would have been interesting to see the split in profits between their smartphones and the rest of the phones they produce. Do they give these numbers in their quarterly reports?

That makes me wonder why there is so much profit in smartphones vs. the rest!? Granted, their price is much higher than that of ordinary phones and thus if the profit percentage is similar, the profit per device is also higher. However, that can't explain it all. Less competition then maybe? Also a bit doubtful as the smartphone market seems to be quite competitive with manufacturers like Nokia, Apple, RIM, HTC (G-phone, WinMob), etc. vying for market share. What do you think?

Every now and then I get an interesting comment for which a typekey id was used as a commenter id instead of an e-mail address. While that is perfectly all right in theory it unfortunately doesn't allow me in practice to reply to you by e-mail in addition to leaving a comment of my own below the poast. That's a bit unfortunate as most people probably won't check back on the blog to see if I have left a response. Therefore, dear readers, please put an e-mail address in the id section of the post if you would like to receive a response in case I have any :-) The e-mail address is only shown to me so there is no need to worry about spam. Thanks!

Here's a quick update on my experience with my netbook, Ubuntu and 3G connectivity. As reported previously, the 3G connectivity manager built into Ubuntu works (most of the time) but doesn't have some important administrative functions included such as network and network type selection and some general observational functions such as current network name and signal strength indications.

At least the later functions are included in the Linux 3G Dashboard from Vodafone Betavine, which works great with my Huawei E220 USB 3G stick. The screenshot on the left shows how signal strength and the network name is displayed in the lower left corner of the dashboard. Nicely done!

What's still missing is a network selection dialogue and to be able to lock the USB stick to 3G, which sometimes helps to stay connected in bad signal conditions. It would be nice to see this in a future version. Also, having the possibility to select a different connection profile on the main screen would also be nice, especially for people (like me) who travel a lot.

I've been thinking a bit about LTE and international roaming lately and just realized that mobile network operators need to come up with a new billing scheme compared to current systems. Here's why:

2G and 3G devices only request the establishment of a data bearer (a PDP context in 3GPP talk, or getting an IP address in Internet talk) when an application requests it for the first time. Thus, from a billing point of view, nothing is charged until that point. With LTE, however, the device gets an IP address right when the device registers with the network after startup. In effect, the 2G / 3G packet call becomes history with LTE. While in the home network this can probably be managed quite well from a billing point of view, I wonder how network operators will proceed for roaming. After all, most users will probably not be too happy to be charged just for switching on their device.

For LTE USB dongles, this might not be a problem as the user can decide whether to plug it in or not. For notebooks with a built-in LTE modem, however, or an LTE capable smartphone, things are different. A user of an LTE capable smartphone probably wants to use it abroad as well, even if it is only for voice calls and the offline organizer functionalities without being charged if he doesn't actively use the Internet. I wonder how this will be solved in practice!?

I could imagine several solutions:

The device detects the roaming scenario and asks the user whether to attach to LTE and get an IP address and warns the user that this might be a chargeable event.

The device detects the roaming scenario and doesn't attach to the LTE network. Instead, a 2G or 3G network is selected where getting an IP address right away is not required. The question then is how the user could trigger this later-on. In case of a smartphone it could wait till an application tries to access the Internet and then reselect to LTE once the connection is established. That won't work for LTE capable notbooks, though, as there are always applications crying for IP connectivity...

The home network detects that the user is roaming and blocks initial access to the Internet. Then, via a web based landing page, the network informs the user that different rates will apply if he proceeds. The problem with this approach is that the user has to open the web browser first before his other applications can get access to the Internet.

A certain amount of data traffic while roaming is already included in the subscription. When going beyond this amount, access is blocked until the user is informed (e.g. via SMS or a landing page) that further Internet access will be billed separately and the user has given his consent.

Switzerland is the latest country for which I have bought a local SIM card for prepaid 3G Internet access while traveling there. Getting the SIM was quick and I was online in less than 5 minutes.

Zurich airport seems to also be a big shopping mall these days and all mobile network operators have a store there. Swisscom has an offer for prepaid 3G Internet access, which, even if it was unintended, is especially interesting for travelers. With the introduction of the iPhone by Swisscom, they also launched a new prepaid tariff which caps Internet charges at 5 Swiss Francs a day. While that is quite a bit if you use it every day, it looks like an acceptable price for occasional use, at least to me. The SIM card is also available separately and can be used with any other device as well.

So after getting into the store, it took only about 5 minutes to get the prepaid SIM. The shop assistant was aware of the Internet tariff and actually what it could be used for. Congrats, I am not quite used to that. Many shop assistants have no clue and will even give out false information such as "it will only work with our phones"...

Their provisioning system is also quick, the SIM card was activated instantly and the tariff option also worked right away. That's how it should be and not like in other countries where activation of an option takes half a day. Kudos to Swisscom, I had a very good customer experience.

Back in April I ran some tests in London to see how many 3G frequencies were used by the carriers there to get a feeling of how much capacity is offered today. To my great surprise, only one of the network operators had deployed more than one 5 MHz carrier frequency. Recently, I was in Vienna and since the country has many affordable 3G Internet offers that lots of people already use, I was wondering if the situation was different.

It turned out that the situation was pretty similar. Except for T-Mobile, who had two 3G carriers deployed in the center of Vienna, all other operators only used one carrier frequency. Network throughput during the day and in the evening in the A1 network were always good (above 1.5 MBit/s) so the current low capacity build-out from an available carrier perspective can handle the traffic well. To me, that sounds like good news!